Bifidobacteria are considered to be probiotics as they are living organisms which exert healthy effects beyond basic nutrition when ingested in sufficient numbers. A high level of ingested bifidobacteria must reach their site of action in order to exert a probiotic effect. A minimum level of approximately 106-107 viable bifidobacteria per gram intestinal contents has been suggested (Bouhnik, Y., Lait 1993). There are reports in the literature which show that in vivo studies completed in adults and in infants indicate that some strains of bifidobacteria are capable of surviving passage through the gastrointestinal tract. Significant differences have been observed between the abilities of different bifidobacteria strains to tolerate acid and bile salts, indicating that survival is an important criterion for the selection of potential probiotic strains.
Ingestion of bifidobacteria can improve gastrointestinal transit and may prevent or assist in the treatment of illnesses which may be caused by deficient or compromised microflora such as gastrointestinal tract (GIT) infections, constipation, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD)—Crohn's disease and ulcerative colitis, food allergies, antibiotic-induced diarrhoea, cardiovascular disease, and certain cancers (e.g. colorectal cancer).
Because of their perceived health-promoting activities, bifidobacteria have in recent years enjoyed an increased amount of scientific scrutiny, which included the full genomic sequencing of a number of strains (reviewed by Liu et al., 2005). These genomic sequences will provide the genetic platforms that allow the study of the molecular mechanisms by which these micro organisms interact with their human host and elicit their probiotic function.